By all the usual rules, it rained long enough and hard enough yesterday to produce a typical gray, miserable, stay-at-home sort of Sunday. But the word apparently never got through to thousands of determined natives and visitors who managed to have a high time in spite of all obstacles.

On the Mall in downtown Washington, the Museum of History and Technology's planned outdoor festival simply moved indoors, and the crowd followed.

A colonial fife and drum corps from Patuxent performed in the museum cafeteria, dressed in ragtag uniforms and bearing muskets, flags and other artifacts of the period.

"It's terrific," said Dorothy Milliken, who had brought her two children despite the rain, "It sends chills up and down your spine."

A dozen members of the Wheelmen, a nationwide group of antique cyclists, did their act in a very confined corner of the museum's ground floor lobby.

"The carpet is very soft," complained Bob Tyler, a schoolteacher from Fredericksburg when he is not riding his 1883 Columbia big-wheeler. "As soon as you take your feet off the pedal, the bicycle starts to slow and it's all you can do to keep from falling."

But the audience seemed undismayed. "This is so neat," said one woman, "I love their outfits!"

Outside the museum's Constitution Avenue entrance, what seemed to be just another ragtag colonial parade turned out on closer inspection, to be the Yippies of Washignton, D.C., marching to the Capitol to demand the legalization of marijuana.

"We smoke herb and we think it's superb," the marchers chanted. "We smoke pot and we like it a lot."

Although many of the approximately 1,300 demonstrators smoked small, hand-rolled cigarettes, there were only a smattering of arrests, most made by U.S. Park Police in the West Potomac Park area at about noon when demonstrators were ordered to remove unauthorized tents from park grounds.

Evicted demonstrators, said they would now have no place to sleep for the rest of their four-day stay in Washington. "The police are trying to provoke a confrontation" said Ange Santilli, a sophomore at Kent State University in Ohio who had hitch-hiked here.

At Wolf Trap Farm Park, about 3,100 bluegrass music lovers - half the park's capacity - showed up for the second annual Bluegrass Music Festival. All but about 200 of the fans enjoyed the concert from dry seats under the covered pavilion.

The die-hards on the soggy lawn insisted, however, that the rain did not bother them.

"Once you get wet, it's just like taking a shower," said Jeff Coopersmith of Potomac, whose only protection from the rain was his hat, which he dubbed the "cheap man's umbrella." Others found ways to clap hands to the music while holding conventional umbrellas.

"Country music people are that kind of mud, rain people," said Irene Tuggle of Vienna when asked why she and seven family members and friends were huddled under a bright blue and yellow striped tent.

Those on the lawn had one advantage over those in the pavilion - they could enjoy their fried chicken, potato salad and drinks while their dry counterparts had to leave the food and drink in the car.

Some events were canceled outright because of yesterday's weather, including the clothesline quilt show in Chantilly, the Chautauqua arts and crafts show at Glen Echo Park in the District, and the Orioles-Red Sox game at Baltimore's Memorial Stadium.

And jack Fuge of the National Weather Service warned that more of the same was in the works. As easterly winds from the ocean cut under warm, moist air aloft, Fuge said. "Rainy and cool weather over Maryland, Delaware and much of Virginia will persist through Monday night and may even continue into the Fourth."